Cash for pounds makes cents in greenback diet

Dieters at the Mayo Clinic in Minnesota apparently think it's worth at least five bucks.

A yearlong study of incentives in dieting found that the majority of 100 obese participants met a goal of losing four pounds per month for a $20 reward -- even at the risk of losing the same amount if they failed.

The study, to be presented this weekend at the American College of Cardiology meeting in San Francisco, found that 62% of those in the incentive program completed the full yearlong study, and averaged a nine-pound weight loss. Only 26% in the group that wasn't offered incentives or penalties completed the program, although they did shed about 2.3 pounds, the study found.

Bribes for blubber is not a new concept. Studies have shown that monetary incentives work, and companies offering weight-loss contests have sprouted.

Steven Driver, an internal medicine resident at the clinic, said the weight-loss industry is "way ahead" of the science on incentivized dieting. "We needed to do some research to see what works," he said.

In a 2008 study in the Journal of the American Medical Assn., 57 overweight and obese people were randomly assigned to monthly weigh-ins, or to a couple of weight-loss incentive programs. One was a lottery, the other a contract that required a deposit. Sure enough, those in the incentive group lost 13 to 14 pounds, compared with about four pounds in the control group.

Roughly half of the incentive group met the study's goal of a pound a week over 16 weeks. Only 11% of the control group met that mark.

The Mayo study went on longer, with incentives continuing for a year. It ended a few months ago, so no follow-ups have been done to check if participants kept the weight off, Driver said.

Participants tended to know they needed to lose weight, but needed some kind of push to go ahead and lose it, Driver said.

Why would a few bucks work? Humans tend to respond to rewards that arrive earlier, and tend to devalue rewards or consequences in the future. Such "hyperbolic discounting" is well-known to psychologists and behavioral economists.

"Our brains have a hard time focusing on distant consequences, as opposed to getting instant gratification," Driver said.

Money is not enough, though, Driver said. All of the participants got some kind of tutoring on diet over a 12-week period, and some were taught behavior-modification methods.

"People still need good advice to stay healthy," he said.

[For the Record, 2:37 p.m. PDT March 18: An earlier version of this online post said 62% of those in the incentive program met or exceeded the weight-loss goal and that 26% in the group that wasn't offered incentives or penalties met their weight-loss goals. The post should have noted that 62% of those in the incentive program completed the full yearlong study and that only 26% in the other group completed the program.]